Method of treating surface of mold and mold having surface treated by said method

ABSTRACT

Provided is a method of treating a surface of a mold to achieve good demoldability and capable of preventing wearing of the mold by avoiding load concentration on one part of the surface of the mold. After a first blasting is performed on the surface of the mold to remove a hardened layer produced on the surface and/or to adjust the surface roughness, a second blasting is performed to create fine irregularities on the surface. Then, an elastic abrasive in which abrasive grains are carried on an elastic body, or a plate-like abrasive having a planar shape with a maximum length that is 1.5 to 100 times the thickness thereof, is ejected onto the surface of the mold at an inclined ejection angle such that the abrasive is caused to slide along the mold surface to flatten peaks of the irregularities created on the mold surface.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of treating a surface of amold, form or die (in the text, called “mold” for both terms) and to amold having a surface treated by said method, and more specifically, itrelates to a method of treating a surface of a mold which can improvethe demoldability of molded products from the mold and to a mold havinga surface treated by this method to achieve excellent demoldability.

2. Description of the Related Art

In case that a mold used for molding metal or resin has roughirregularities on its molding surface, such irregularities aretransferred to a molded product (workpiece). Thus, finishing of thesurface of the workpiece is required after molding. In addition, becausethe surface of the workpiece is engaged with the irregularities on thesurface of the mold, which decreases the demoldability, the productivitysignificantly decreases during molding.

Therefore, typically, surfaces of molds are polished to a mirror finishby hand. This not only enables works to be finished in smooth surfaces,but also provides the required demoldability for works.

However, in recent years, the number of molds having a complex shape hasbeen increasing, and demands for quick delivery of molds are rising.Thus, mirror-polishing of surfaces of molds by hand, which consumes alot of time and effort, is an obstacle to meeting such demands andcauses an increase in fabrication cost of the molds.

Moreover, depending on the shape and material of workpieces to bemolded, the required demoldability cannot always be obtained even bymirror-polishing of surfaces of molds.

Thus, methods that can be substituted for mirror-polishing by hand havebeen proposed to improve the demoldability of works. Examples of suchmethods include increasing the draft angle of a cavity of a mold andsubjecting the surface of the mold to treatment for improving slip,e.g., forming a diamond-like carbon film (DLC).

In contrast to applying a mirror finish to a surface of a mold, methodsin which irregularities having a predetermined shape are formed on asurface of a mold have been proposed. An example of such methods isejecting spherical abrasive particles at high speed onto the surface ofthe mold for molding rubber products to create spherical dimples with adiameter of from 10 μm to 30 μm, and then forming a hard chromiumcoating thereon (see claim 1 of the Publication of Japanese Patent No.3154033).

The reasons for applying a mirror finish to a surface of a mold asdescribed above are that, irregularities occurring on the surface of themold are transferred to the surface of a workpiece, forming unwantedirregularities on the surface of the workpiece, and that the workpiececannot be removed from the mold (for example, the workpiece cannot bemoved parallel to the surface of the cavity of the mold) if theirregularities on the surface of the mold are engaged with theirregularities on the surface of the workpiece transferred from themold.

On the other hand, excellent demoldability cannot always be obtained bymirror-finished surfaces of molds. According to one report, thedemoldability can be improved by forming relatively fine recesses in thesurface of the mold in the case of molding rubber products for cars (seethe Publication of Japanese Patent No. 3154033).

However, when recesses are formed by blasting as described in theaforementioned Publication of Japanese Patent No. 3154033, not only arerecesses formed in the surface of the mold by the collision of sphericalabrasive particles, but also protrusions appear on the surface of themold as a result of the base material of the mold being pushed out bythe collision of the abrasive particles (see the enlarged view in FIG.1B).

The protrusions generated in this way makes inroads into the surface ofthe workpiece produced by molding and thus interfere with the workpiecewhen the workpiece is removed from the mold, which decreases thedemoldability.

Furthermore, when recesses are formed by the above-described method, thesharp protrusions generated simultaneously with the recesses serve ascontact portions with the surface of the workpiece which make slidingcontact with the surface of the mold when the workpiece is removed fromthe mold. Thus, the surface of the mold comes into point contact withthe workpiece, leaving scratches on the surface of the workpiece whenthe workpiece is removed from the mold. Furthermore, because the load isconcentrated on the peaks of the protrusions, the surface of the mold iseasily worn.

Accordingly, an object of the present invention is to provide advantagesin that improved demoldability achieved by creating irregularities arefurther enhanced by creating, on the mold surface, irregularities withthe peaks being evened out and flattened by a blasting, that the surfaceof the workpiece is prevented from being scratched, and that wear of themold is prevented by avoiding load concentration on one part of thesurface of the mold with relative ease and without the need forlaborious work such as polishing by hand.

SUMMARY OF THE INVENTION

In order to achieve the above objective, a method of treating a surfaceof a mold according to the present invention is characterized bycomprising the steps of subjecting the surface of the mold to:

a first blasting for removing a hardened layer produced on the surfaceand/or for adjusting the surface roughness;

a second blasting for creating fine irregularities on the surface; and

a third blasting for flattening peaks of the irregularities created onthe surface, the third blasting being performed by causing an ejectedabrasive to slide along the surface of the mold.

In the method of treating the surface of the mold described above, thethird blasting may be performed by ejecting an elastic abrasive in whichabrasive grains are kneaded in an elastic body and/or abrasive grainsare carried on a surface of the elastic body onto the surface of themold at an inclined incidence angle.

Alternatively, instead of ejecting the elastic abrasive, the thirdblasting may be performed by ejecting a plate-like abrasive having aplanar shape with a maximum length that is 1.5 to 100 times thethickness thereof onto the surface of the mold at an inclined incidenceangle.

Furthermore, in the method of treating the surface of the mold, thefirst blasting may be performed so that the ejected abrasive is causedto slide along the surface of the mold.

In such case, same as the third blasting, the first blasting may beperformed by ejecting the elastic abrasive in which abrasive grains arekneaded in an elastic body and/or abrasive grains are carried on asurface of the elastic body onto the surface of the mold at an inclinedincidence angle in the first blasting, alternatively, the first blastingmay be performed by ejecting a plate-like abrasive having a planar shapewith a maximum length that is 1.5 to 100 times the thickness thereof isonto the surface of the mold at an inclined incidence angle.

Furthermore, in any of the above mentioned methods of treating thesurface of the mold, the second blasting may be performed by ejecting aspherical abrasive, and in the case, it is preferable that the secondblasting be performed until a coverage of 100% is achieved.

Alternatively, instead of ejecting the spherical abrasive, the secondblasting may be performed by ejecting a grit-like abrasive, and in thecase, it is preferable that the second blasting be performed until acoverage of 60% to 100% is achieved.

Furthermore, the present invention also relates to a mold having asurface treated by any of the above mentioned methods and characterizedin that the distribution of heights of 70% or more in the surface of themold in the load curve is 70% or more.

With the above-described configuration of the present invention, byusing the surface treatment method of the present invention, recessesthat can improve the demoldability can be formed on a surface of a moldby a relatively easy procedure, namely, a blasting, without the need forlaborious work such as polishing the surface of the mold by hand to amirror finish.

Moreover, because the peaks of the portions between the recesses formedin this way are evened out and flattened, the mold does not leavescratches on the surface of the workpiece when it comes into contactwith the workpiece. Furthermore, rapid wearing of the surface of themold resulting from load concentration due to contact with the surfaceof the workpiece can be prevented.

By ejecting an elastic abrasive or a plate-like abrasive at the surfaceof the mold at an inclined incidence angle in a third blasting, theabrasive can be relatively easily made to slide along the surface of themold. Thus, the peaks of the irregularities on the surface of the moldresulting from a second blasting can be easily removed and evened out.

Furthermore, by ejecting an elastic abrasive or a plate-like abrasiveonto the surface of the mold at an inclined incidence angle in a firstblasting similarly to the above, a surface-hardened layer can be easilyremoved, and the surface of the mold can be easily evened out.

Note that, when a spherical abrasive is ejected onto the surface of themold in the second blasting, in particular, when the spherical abrasiveis ejected such that a coverage of 100% is achieved, the width (denotedby W in the enlarged view in FIG. 1C) of the contact portion of thesurface of the mold with the workpiece is relatively narrow. Thus, notonly is the contact resistance when the workpiece is removed from themold significantly reduced, but also air and a demolding agent caneasily flow into the recesses.

On the other hand, when grit which is a polygonal abrasive is ejectedonto the surface of the mold in the second blasting, in particular, whengrit is ejected such that a coverage of 60% to 100% is achieved, thewidth of the contact portion of the surface of the mold (W in theenlarged view in FIG. 2C) with the workpiece is relatively large.However, because the sharp peaks of the protrusions have been removed,stress concentration is less likely to occur. Furthermore, because therecesses in the surface of the mold are scattered, air and a demoldingagent can be easily trapped in the recesses during molding.

As a result, the demoldability of works can be significantly improved inany case.

That is, the presence of the recesses makes it easy for a demoldingagent to be deposited and held on the surface of the mold, and thepresence of the recesses also prevents the workpiece from sticking tothe surface of the mold and allows the workpiece to slide easily.Moreover, because the contact area between the workpiece and the surfaceof the mold is reduced, the frictional resistance decreases. Again,there are advantages in that the workpiece is prevented from beingengaged with the peaks of the protrusions of the mold, that the recessestrap gas (air and other gases), and that the friction is reduced. Thus,the demolding resistance is reduced. As a result, the demoldability aresignificantly improved.

According to formation of such recesses, an insulation effect isprovided by the presence of air traps or oil traps, thereby heatconduction can be prevented. Thus, the mold is less likely to conductheat to the workpiece and is less likely to be cooled. As a result, whenmolding is continuously performed using the same mold, the time forheating the mold for the next molding can be reduced. Thus, theproductivity can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and advantages of the invention will become apparent fromthe following detailed description of preferred embodiments thereofprovided in connection with the accompanying drawings in which:

FIGS. 1A to 1C are diagrams schematically showing a method of treating asurface of a mold of the present invention, in which FIG. 1A shows afirst blasting, FIG. 1B shows a second blasting, and FIG. 1C shows athird blasting;

FIGS. 2A to 2C are diagrams schematically showing another method oftreating a surface of a mold of the present invention, in which FIG. 2Ashows a first blasting, 2B shows a second blasting, and 2C shows a thirdblasting;

FIG. 3 is a diagram showing load curves; and

FIG. 4 is a diagram showing a load length ratio.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described below withreference to the attached drawings.

Outline of Surface Treatment Method

A method of treating a surface of a mold of the present inventionincludes the steps of subjecting the surface of the mold (the surface ofa portion that comes into contact with the workpiece) to be treated to afirst blasting for removing a surface-hardened layer generated when themold is fabricated and/or for adjusting the surface roughness, e.g.,flattening; a second blasting for creating fine irregularities on thesurface of the mold after the first blasting; and a third blasting forflattening peaks of the irregularities created on the surface of themold after the second blasting.

Object to be Treated (Mold)

The surface treatment method of the present invention is widely intendedfor products that are generally called “molds”, and various molds can betreated without limiting the use of the molds.

Examples of the mold that can be treated by the surface treatment methodof the present invention include various molding dies intended for metalprocessing, in which the molding load is high; open-type molding dies inwhich a material is held between upper and lower molds; molds intendedfor metal casting or resin molding, in which the molding load isrelatively low; closed-type molds in which a material is injected into aclosed mold; and molds for press-molding.

In particular, the present invention is effective for the surfacetreatment of a mold that is used to mold a workpiece made of metal orhard resin that, unlike elastic material such as rubber or elastomer,cannot be removed from the mold due to engagement of their shapes whenthe surface shape of the workpiece is molded so as to conform to thesurface shape of the mold.

However, the surface treatment method of the present invention may beperformed on a mold that is used to mold a workpiece made of elasticmaterial such as rubber or elastomer.

First Blasting

First, a first blasting is performed on a mold to be treated, at leaston the surface of a portion in contact with a workpiece, e.g., thesurface of a cavity in the case where the mold is the above-describedone (see FIGS. 1A and 2A).

The first blasting is performed to improve the surface of the mold. Thisblasting is so-called base treatment for improving the surface conditionof the mold, in which a surface-hardened layer such as an arc-hardenedlayer generated when the mold is fabricated is removed, and tool marks(for example, irregularities resulting from processing marks generatedalong the path of movement of a cutting tool) are removed to flatten thesurface of the mold.

This first blasting can be performed by a typical blasting known as a“blasting” or “sand-blasting”. The material and particle diameter of theabrasive to be used and the processing conditions such as the ejectionpressure and the processing duration can be selected from various knownmaterials, particle diameters, and processing conditions according tothe material and use of the mold to be treated.

The first blasting may include several steps, in which, for example, theparticle diameter of the abrasive to be used and/or the ejectionpressure is gradually reduced.

The first blasting may include, instead of or in addition to theabove-mentioned typical known blasting, treatment for flattening thesurface by causing the ejected abrasive to slide along the surface ofthe mold.

Examples of the abrasive that is caused to slide along the surface ofthe mold include an elastic abrasive in which an abrasive is carried onthe surface of an elastic material (an elastic body, such as rubber orelastomer, a resin foam, or another viscoelastic body, such as a crushedrhizome of plant, devil's tongue, or gelatin) and/or in which anabrasive is kneaded in such an elastic material. This elastic abrasivecan be ejected onto the surface of the mold at an inclined ejectionangle of for example, less than 90°, and more preferably, at aninclination angle X of 0°≦X≦80°.

Alternatively, instead of the above-mentioned elastic abrasive,plate-like abrasive having a planar shape with a maximum length of fromabout 0.05 mm to 10 mm, which is 1.5 to 100 times the thickness thereof,the plate-like abrasive being made of abrasive grains themselves formedin a planar shape, abrasive grains bonded by a binder and formed in aplanar shape, or a planar base material (paper, metal, resin, or thelike) carrying abrasive grains on the surface thereof and/or a planarbase material in which abrasive grains are kneaded, may be ejected ontothe surface of the mold at the same inclined ejection angle as describedabove.

Thus, the abrasive upon colliding with the surface of the mold can becaused to slide along the surface of the mold, thereby improving thesurface of the mold to a flat surface free of tool marks and the like.Furthermore, a hard film or the like can be removed if there is any sucha film formed on the surface of the mold.

Second Blasting

After the first blasting is performed on the surface of the mold toimprove the surface as described above, a second blasting for formingpredetermined recesses on the surface of the mold is performed.

When forming hemispherical recesses in the second blasting, a sphericalabrasive made of metal, ceramic, glass, cemented carbide, or the likehaving an average particle diameter of from 10 μm to 100 μm is ejectedto create fine irregularities including hemispherical recesses on thesurface of the mold (see FIG. 18).

When the recesses to be formed are hemispherical recesses, it ispreferable that such recesses be formed on the surface of the mold suchthat the percentage of the area of the surface of the mold covered bydents (herein called “coverage”) of from 60% to 100% is achieved.

Furthermore, the irregularities do not necessarily have to be created byejecting the above-mentioned spherical abrasive in the second blasting,but may be created by ejecting grit which is a polygonal abrasive (seeFIG. 2B). In such a case, grit having an average particle diameter offrom 10 μm to 100 μm (for example, a grit composed of alundum,carborundum, zircon, glass, metal, cemented carbide or the like) isejected on the surface of the mold to create irregularities.

In the case of creating irregularities on the surface of the mold byejecting grit as described above, it is preferable that a coverage offrom 60% to 100% be achieved.

Third Blasting

When the spherical abrasive is caused to collide with the surface of themold to create irregularities thereon in the second blasting asdescribed above, protrusions protruding from the surface of the mold areformed by the base material of the mold being pushed out duringcollision of the spherical abrasive, as shown in the enlarged view inFIG. 1B. In particular, when the spherical abrasive is caused to collidewith the surface of the mold until a coverage of 100% is achieved, thespherical abrasive collides with already formed protrusions, making theshape of the protrusions complex.

Furthermore, when the grit-like abrasive is caused to collide with thesurface of the mold to create irregularities on the surface of the moldin the second blasting, recesses which are portions cut away by thecollision of the abrasive, and protrusions which are portions remainingwithout being cut away, are formed as shown in FIG. 2B.

Therefore, even when the first blasting for flattening is performed inadvance, the peaks of the irregularities created on the surface of themold come into point contact with the workpiece, decreasing thedemoldability of the workpiece and leaving scratches on the surface ofthe workpiece. In addition, the surface of the mold is rapidly wornbecause the load is concentrated on the peaks when the mold slides alongthe surface of the workpiece.

Accordingly, a third blasting in this step is performed on theirregularities created on the surface of the mold to flatten the peaksby removing the protrusions at a certain height (dotted line portions inenlarged views in FIGS. 1C and 2C show examples), while leaving therecesses that trap a demolding agent and air, as shown in enlarged viewsin FIG. 1C and FIG. 2C.

In the third blasting, the ejected abrasive is caused to slide along thesurface of the mold to flatten the peaks of the protrusions.

Examples of the abrasive that is caused to slide include the abrasivethat is caused to slide along the surface of the mold, similarly to theabove-described first blasting. For example, an elastic abrasive inwhich an abrasive having an average particle diameter of from 1 μm to 50μm is carried on the surface of an elastic material, and/or an elasticabrasive in which such abrasive is kneaded in the elastic material, orplate-like abrasive having a planar shape with a maximum length of fromabout 0.05 mm to 10 mm, which is 1.5 to 100 times the thickness thereof,may be used. By ejecting such abrasive onto the surface of the mold atan angle of less than 90°, more preferably, at an inclination angle X of0°≦X≦80°, the ejected abrasive can be caused to slide along the surfaceof the mold. Thus, portions near the peaks of the protrusions can beremoved at a substantially constant height, whereby the demoldability ofworks can be improved, and local load concentration can be prevented.

Surface Shape of Mold

When the spherical abrasive is ejected in the second blasting as shownin the enlarged view in FIG. 1C, hemispherical recesses with an openingdiameter R of from 10 μm to 150 μm and a depth D of from 2 μm to 20 μmare provided in the surface of the mold after being subjected to thesurface treatment as described above. Flat portions with a width W offrom 20 μm to 60 μm are formed at the tips of the protrusions betweenthe recesses.

On the other hand, when the grit-like abrasive is used in the secondblasting as shown in the enlarged view in FIG. 2C, recesses having sharpbottoms, with an opening width R of from 5 μm to 50 μm and a depth D offrom 5 μm to 60 μm, are formed. Flat portions with a width W of from 20μM to 100 μM are formed at the tips of protrusions between the recesses.

In either of the surface of the molds formed as described above, therecesses are preferably created such that the distribution of heights of70% or more in the load curve is 70% or more.

Herein, the term “load curve” refers to a graph in which the value ofthe load length ratio (tp) is plotted on the horizontal axis, and theheight of the measurement curve which means the height of cutting isplotted on the vertical axis (see FIG. 3). The term “load length ratio(tp)” refers to a ratio described as a percentage of the total cutlength (also referred to as “load length ηp”) which is obtained byextracting a reference length L in the direction of the average linefrom the roughness curve, and by cutting the roughness curve of theextracted portion at a cut level parallel to the peak line, with respectto the reference length. The “load length ratio (tp)” indicates bothinformation in the height direction and information in the horizontaldirection, in which both tp**% and cut level c μm or c % which ispercentage with respect to Ry are described (see FIG. 4) (JISB0601-1994).

Note that FIGS. 3 and 4 are used only for describing the concept of the“load curve” and the “load length ratio”, and the graphs in FIGS. 3 and4 do not indicate the conditions of the surface of the mold treated bythe method of the present invention.

On the surfaces of the molds configured as described above, in both ofthe configuration shown in FIG. 1C in which hemispherical recesses areformed, and the configuration shown in FIG. 2C in which recesses havingsharp bottoms are formed, the peaks of the protrusions are evened outflatly. Thus, engagement with the surface of the workpiece can beprevented, and load concentration can be prevented.

Note that, in the configuration shown in FIG. 1C in which hemisphericalrecesses are formed, the width W of the portions that come into contactwith the surface of the workpiece is relatively small. As a result, thelikelihood of load concentration slightly increases. However, becauseair and a demolding agent can easily flow into the recesses, thedemoldability are improved.

In contrast, on the surface of the mold shown in FIG. 2C, in whichrecesses having sharp bottoms are formed, the width W at the peaks thatcome into contact with the workpiece is relatively large. Thus, comparedwith the case where the hemispherical recesses are formed as describedabove, the contact resistance is large, however, stress concentration isless likely to occur, and, because the recesses on the surface of themold are scattered in this configuration, therefore, air and a demoldingagent are easily trapped in the recesses, and the air and the demoldingagent once trapped therein, tend to remain.

As a result, in both of the cases where hemispherical recesses areformed as shown in FIG. 1C, and where recesses having sharp bottoms areformed as shown in FIG. 2C, excellent demoldability can be exhibited.

Processing Example   Object to be treated Mold   Material of mold SKD61  Mold diameter of core pin Φ30 mm, length 60 mm, and draft angle 0°  Workpiece for injection molding made of POM (polyacetal) outsidediameter Φ34 mm, inside diameter Φ30 mm, length 25 mm (1) ComparativeExample Ground finish (finished by a grinder)   Surface roughness Ra(μm): 0.100 μm (2) Example 1 (hemispherical recesses are formed)  Object to be treated Same as comparative example   Blasting apparatusPneuma-blaster SGK-3 (suction type) manufactured by Fuji ManufacturingCo., Ltd.    (1) First Blasting      Abrasive FUJIRANDOM WA#220 (averageparticle diameter 60 μm)      Ejection pressure 0.3 MPa    (2) SecondBlasting      Abrasive Fuji glass beads FGB#320 (spherical glass beads;average particle diameter 40 μm)      Ejection pressure 0.3 MPa    (3)Third Blasting      Blasting apparatus LDQ-SR-3 (blower type)manufactured by Fuji Manufacturing Co., Ltd.      Abrasive Elastic body(rubber) with abrasive grains (silicon carbide #3000 having an averageparticle diameter of 4 μm) kneaded therein      Ejection pressure 0.06MPa      Ejection angle 30°      Surface roughness Ra: 0.09 μm (3)Example 2 (recesses having sharp bottoms are formed)   Object to betreated Same as comparative example   Blasting apparatus Pneuma-blasterSGK-3 manufactured by Fuji Manufacturing Co., Ltd.    (1) First Blasting     Abrasive FUJIRANDOM WA#220 (average particle diameter 60 μm)     Ejection pressure 0.3 MPa    (2) Second Blasting      AbrasiveFUJIRANDOM #400 (average particle diameter 30 μm)      Ejection pressure0.3 MPa    (3) Third Blasting      Blasting apparatus LDQ-SR-3 (blowertype) manufactured by Fuji Manufacturing Co., Ltd.      Abrasive Elasticbody (rubber) with abrasive grains (silicon carbide #3000 having anaverage particle diameter of 4 μm) kneaded therein      Ejectionpressure 0.06 MPa      Ejection angle 30°      Surface roughness Ra:0.11 μm (4) Measurement of demolding resistance      The demoldingresistance in the above-described Comparative Example and Examples weremeasured. Demolding resistance Comparative Example 1 Example 1 0.2Example 2 0.25 (The demolding resistance demolding resistance weremeasured using a piezoelectric quartz-crystal sensor manufactured byKistler Japan Co., Ltd.; Comparative Example was assumed to be 1.0)

From the above descriptions, it is understood that the demoldingresistance is as low as from 20% to 25% of that of the ComparativeExample, although the example of the present invention is not sodifferent from the Comparative Example in terms of surface roughness.

In this specification and claims, “mold” includes “mold and die”, “form”or “die”.

Thus the broadest claims that follow are not directed to a machine thatis configured in a specific way. Instead, said broadest claims areintended to protect the heart or essence of this breakthrough invention.This invention is clearly new and useful. Moreover, it was not obviousto those of ordinary skill in the art at the time it was made, in viewof the prior art when considered as a whole.

Moreover, in view of the revolutionary nature of this invention, it isclearly a pioneering invention. As such, the claims that follow areentitled to very broad interpretation so as to protect the heart of thisinvention, as a matter of law.

It will thus be seen that the objects set forth above, and those madeapparent from the foregoing description, are efficiently attained andsince certain changes may be made in the above construction withoutdeparting from the scope of the invention, it is intended that allmatters contained in the foregoing description or shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense.

It is also to be understood that the following claims are intended tocover all of the generic and specific features of the invention hereindescribed, and all statements of the scope of the invention which, as amatter of language, might be said to fall therebetween.

Now that the invention has been described;

What is claimed is:
 1. A mold having fine recesses in a surface thereof,the recesses being formed by a method comprising subjecting the surfaceof the mold to: a first blasting performed by ejecting an elasticabrasive in which abrasive grains are kneaded in an elastic body and/orabrasive grains are carried on a surface of the elastic body onto thesurface of the mold at an inclined incidence angle for removing ahardened layer produced on the surface and/or for adjusting the surfaceroughness; a second blasting for creating fine irregularities on thesurface by ejecting abrasives onto the surface of the mold; and a thirdblasting for flattening peaks of protrusions of the irregularitiescreated on the surface, the third blasting being performed by causing anejected abrasive to slide along the surface of the mold, wherein saidsurface of said mold comprises flat portions each with a width W of from20 μm to 100 μm in which peaks of the protrusions exceeding apredetermined height between the recesses are evened out and flattened.2. The mold according to claim 1, wherein the fine irregularitiesincluding the recesses, wherein each of said recesses has ahemispherical shape, are formed on the surface by performing the secondblasting by ejecting a spherical abrasive.
 3. The mold according toclaim 2, wherein the recesses are created such that the distribution ofheights of 70% or more in a load curve for the surface of the mold is70% or more.
 4. The mold according to claim 2, wherein hemisphericalrecesses with an opening diameter R of from 10 μm to 150 μm and a depthD of from 2 μm to 20 μm are provided in the surface of the mold afterbeing subjected to the first to third blastings.
 5. The mold accordingto claim 2, wherein flat portions each having a width W of from 20 μm to60 μm are formed at the tips of the protrusions between the recesses. 6.The mold according to claim 2, wherein the fine irregularities areformed on the surface by performing the second blasting until a coverageof 100% is achieved.
 7. The mold according to claim 1, wherein the fineirregularities including the recesses, wherein each of said recesses hassharp bottoms, are formed on the surface by performing the secondblasting by ejecting a grit-like abrasive.
 8. The mold according toclaim 7, wherein the recesses are created such that the distribution ofheights of 70% or more in a load curve for the surface of the mold is70% or more.
 9. The mold according to claim 7, wherein recesses eachhaving sharp bottoms, with an opening width R of from 5 μm to 50 μm anda depth D of from 5 μm to 60 μm, are formed.
 10. The mold according toclaim 7, wherein the fine irregularities are formed on the surface byperforming the second blasting until a coverage of 60% to 100% isachieved.
 11. The mold according to claim 1, wherein the recesses arecreated such that the distribution of heights of 70% or more in a loadcurve for the surface of the mold is 70% or more.
 12. The mold accordingto claim 1, wherein the peaks of the protrusions between the recessesare evened out and flattened by ejecting an elastic abrasive in whichabrasive grains are kneaded in an elastic body and/or abrasive grainsare carried on a surface of the elastic body onto the surface of themold at an inclined incidence angle as the third blasting.
 13. The moldaccording to claim 12, wherein the fine irregularities are formed on thesurface by performing the second blasting by ejecting a sphericalabrasive.
 14. The mold according to claim 12, wherein the fineirregularities are formed on the surface by performing the secondblasting by ejecting a grit-like abrasive.
 15. The mold according toclaim 1, wherein the peaks of the protrusions between the recesses areevened out and flattened by performing the third blasting by ejecting aplate-like abrasive having a planar shape with a maximum length that is1.5 to 100 times the thickness thereof onto the surface of the mold atan inclined incidence angle.
 16. The mold according to claim 1, whereinthe hardened layer produced on the surface and/or for adjusting thesurface roughness are removed by performing the first blasting so thatthe ejected abrasive is caused to slide along the surface of the mold.